Phased array radars are well known and are widely used in various configurations for target acquisition purposes. In each case, their basic construction has many similarities and invariably includes an antenna consisting of an array of identical radiators. To operate the system, power is fed to these radiators and the direction at which the beam is radiated from the antenna is controlled with electronic means by altering the phase of the power that is fed to each of the individual radiators. Thus, no mechanical movement is necessary to change the direction of the beam.
Due to speed and accuracy requirements, the design for many configurations of a phased array radar have tended to be rather sophisticated. Typically, there is a central power feed, with cascading transmission lines connecting the power feed to each of the radiators. Also there is typically a separate dedicated phase shifter which is incorporated into the particular transmission line for each radiator. One reason for this particular architecture is that it minimizes the additive effect of potential inaccuracies in the phase shifters. As should be expected, however, this architecture can be expensive and can be very difficult to manufacture. This is particularly so where very short wavelengths are to be used due to the fact the sizes for the radar's components must be appropriately scaled to the wavelength.
It happens, however, that there are some applications for phased array antennas wherein very short wavelengths are acceptable, and may even be desirable. Furthermore, for some applications it is possible to sacrifice some accuracy and speed of response time without denigrating overall system performance. For example, consider the collision avoidance problems confronted by relatively slow moving vehicles such as cars, boats, and light aircraft.
In light of the above, it is an object of the present invention to provide a phase shifter assembly for a phased array radar which is effective for use with relatively short wavelengths in applications where there can be some sacrifice in speed and accuracy requirements. It is also an object of the present invention to provide a phase shifter assembly for a phased array radar which uses a common power feed that is serially connected via a transmission line to each of a plurality of phase shifter subarrays through power splitters/combiners which are tailored to provide the exact attenuation per subarray for optimum beam shape. Another object of the present invention is to provide a phase shifter assembly for a phased array radar which uses a common driver to activate a plurality of alignment phase shifters in the power transmission line for aligning adjacent subarrays in the antenna to establish a substantially continuous wave front for the beam which is radiated from the antenna. Yet another object of the present invention is to provide a phase shifter assembly for a phased array radar which uses a common driver to serially activate the individual phase shifter elements in each phase shifter subarray to direct the beam which is radiated from the antenna. Still another object of the present invention is to provide a phase shifter assembly for a phased array radar which is characterized by mechanical simplicity. Another object of the present invention is to provide a phase shifter assembly for a phased array radar which is relatively easy to manufacture, simple to operate and comparatively cost effective.